1899] MICROSCOPICAL JOURNAL. 271 



under varying conditions of temperature and moisture. 

 Thus the development of atypical forms and changes in 

 the virulence of the bacillus due to its mode of life out- 

 side the body may be detected by such a succession of 

 cultures starting from a single one. 



This is the laboratory side of the question, as yet un- 

 worked, except in desultory and fragmentary fashion. 

 Leading up to it from the side of the practical work of 

 the health board, is the identification of such culture 

 material, and its proper disinfection, or destruction. In 

 the experience of the writer a drain pipe that is rarely if 

 ever flushed completely, and that is crusted over on the 

 inside with partly dried filth is specially apt to form a 

 medium for the retention and growth of successive crops 

 of the diphtheria bacillus. Inoculation may occur in va- 

 rious ways, a little expectoration, rinsing the mouth at 

 the kitchen sink, for example, may start the process. The 

 bacilli implanted in an underground drain, or other re- 

 ceptacle that is constantly nearly dry, and never com- 

 pletely flushed, find these conditions very suitable for 

 their growth. The temperature and moisture, and fresh 

 accessions of organic matter from day to day are well 

 adapted to bring about a series of cultures resembling 

 substantially those from tube to tube suggested in the last 

 paragraph. In such a case disinfectant solutions may 

 run along the bottom of the drain leaving the top and 

 sides untouched. Indeed in the case of a very large 

 drain of this sort the writer found it necessary to gene- 

 rate chlorine in order to disinfect it completely. During 

 continuance of infection there is constant liability of its 

 diffusion by the partly dried material becoming detached 

 and carried by the vapors arising from fermentation, or 

 by access of air currents. An instance of this sort that 

 came under the observation of the writer was in connec- 

 tion with a dry closet system, so-called, in a school build- 

 ing. The vaults containing the partly dried excretions 



